[QE-users] Double x-coordinate in bands.x output

[Lorenzo Paulatto]

If two consecutive points are "very" far away, the bands (?) code 
assumes that you made a jump in the path and put them with the same path 
coordinate. How far is "very" far is defined i na funny way: if thw new 
step is twice as large as the previous one:

IF(dxmod >5*dxmod_save) THEN
!
!   A big jumpin dxmod is a sign that the point xk(:,n) and xk(:,n-1)
!   are quite distant and belong to two different lines. We put them on
!   the same point in the graph

(bands.f90 line 564)

You can tweak the code, or tweak your path.

cheers


On 12/07/2022 12:09, Carl-Friedrich Schön wrote:
>
> Dear all,
>
> I have calculated the band structure for Si with 8 atoms in the UC 
> (conventional standard from MP) using QE6.4.
>
> My input is:
>
> /&control//
> // calculation = 'bands'//
> // prefix='Si_mp-149_conventional_standard'//
> // tstress = .true.//
> // tprnfor = .true.//
> // pseudo_dir='/rwthfs/rz/cluster/home/cs825852/DFT/UPF_Ressources_NSCF/NC'//
> // outdir='tmp'//
> // disk_io='low'//
> // wf_collect=.true.//
> /// //
> //&system//
> // ibrav =0,//
> // nat=8//
> // ntyp=1//
> // ecutwfc = 100//
> // ecutrho = 400//
> // occupations = 'fixed'//
> // nbnd = 24//
> /// //
> //&electrons//
> // mixing_beta = 0.2//
> // conv_thr = 1.0d-10//
> /// //
> //ATOMIC_SPECIES//
> //Si 28.086 Si.upf//
> //ATOMIC_POSITIONS {crystal}//
> //Si  0.25  0.75  0.25//
> //Si  -0.0  -0.0  0.5//
> //Si  0.25  0.25  0.75//
> //Si  -0.0  0.5  0.0//
> //Si  0.75  0.75  0.75//
> //Si  0.5  0.0  0.0//
> //Si  0.75  0.25  0.25//
> //Si  0.5  0.5  0.5//
> //CELL_PARAMETERS//
> //10.334398  0.0  0.0//
> //0.0  10.334398  0.0//
> //0.0  0.0  10.334398//
> //K_POINTS {crystal_b}//
> //12//
> //0.0  0.0  0.0  20.0//
> //0.5  0.0  0.5  20.0//
> //0.5  0.25  0.75  20.0//
> //0.375  0.375  0.75  20.0//
> //0.0  0.0  0.0  20.0//
> //0.5  0.5  0.5  20.0//
> //0.625  0.25  0.625  20.0//
> //0.5  0.25  0.75  20.0//
> //0.5  0.5  0.5  20.0//
> //0.375  0.375  0.75  20.0//
> //0.625  0.25  0.625  20.0//
> //0.5  0.0  0.5  20.0/
>
> My bands.x output however states:
>
> /high-symmetry point:  0.0000 0.0000 0.0000   x coordinate   0.0000//
> //     high-symmetry point:  0.5000 0.0000 0.5000   x coordinate   
> 0.7071//
> //     high-symmetry point:  0.5000 0.2500 0.7500   x coordinate   
> 1.0607//
> //     high-symmetry point:  0.3750 0.3750 0.7500   x coordinate   
> 1.2374//
> //     high-symmetry point:  0.0000 0.0000 0.0000   x coordinate   
> 1.2374//
> //     high-symmetry point:  0.5000 0.5000 0.5000   x coordinate   
> 2.1035//
> //     high-symmetry point:  0.6250 0.2500 0.6250   x coordinate   
> 2.4096//
> //     high-symmetry point:  0.5000 0.2500 0.7500   x coordinate   
> 2.5864//
> //     high-symmetry point:  0.5000 0.5000 0.5000   x coordinate   
> 2.9400//
> //     high-symmetry point:  0.3750 0.3750 0.7500   x coordinate   
> 3.2462//
> //     high-symmetry point:  0.6250 0.2500 0.6250   x coordinate   
> 3.5524//
> //     high-symmetry point:  0.5000 0.0000 0.5000   x coordinate   3.8585/
>
> As you can see, the fourth and fifth KPoint have the same x 
> coordinate, while they are not identical.
>
> The .gnu output seems to state the correct energies, while the 
> x-coordinate just stays identical for this range:
>
> /    1.2198   -4.4150//
> //    1.2286   -4.4160//
> //    1.2374   -4.4163//
> //    1.2374   -4.4466//
> //    1.2374   -4.4594//
> //    1.2374   -4.4544//
> //    1.2374   -4.4316//
> //    1.2374   -4.3909/
>
> /..../
>
> I had the same issue occur with Cu (mp-30).
>
> While I have found some outputs with the same problem (?) online, it 
> was the topic of the discussion.
>
> Is this a bug, or am I missing/misunderstanding some intended behavior?
>
> Thanks and best,
>
> Carl-Friedrich Schön, PhD Student, RWTH Aachen
>
>
> _______________________________________________
> The Quantum ESPRESSO community stands by the Ukrainian
> people and expresses its concerns about the devastating
> effects that the Russian military offensive has on their
> country and on the free and peaceful scientific, cultural,
> and economic cooperation amongst peoples
> _______________________________________________
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
> users mailing listusers at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users
-- 
Dr. Lorenzo Paulatto
IdR @ IMPMC - CNRS UMR 7590 & Sorbonne Université
phone: +33 (0)1 442 79822 / skype: paulatz
http://www.impmc.upmc.fr/~paulatto/ - https://anharmonic.github.io/
23-24/423 B115, 4 place Jussieu 75252 Paris CX 05
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20220712/7862c7ab/attachment.html>